Electric meter.



K. SCHMIEDEL.

ELECTRIC METER.

APPUCATION FILED 050.1.1914.

1,201,639. Patented Oct. 17,1916.

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Witnesses: Inventor:

W Karl Schmjedel HxsAttorneg.

m was PETERS cc PNOYWLITNO" WASHING MN. :1. c.

K. SCHMIEDEL.

ELECTRIC METER.

APPLICATION FILED DEC- 7| I914. 1,201,639. 7 Patented Oct. 17,1916.

- 2 SHEETS-SHEET 2- 1 12.5. 'Q'

Witnesses. Im/entori I Karl Schmieolel HzsAttorneg.

KARL SCHMIEDEL, 01E CHARLOTTENBURG, GE RMANYQASSIGNOR GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

ELECTRIC METER.

Specification of Letters Patent.

Patented Oct. 17, 191 6.

TooZZ whom it may concern:

Be it known that I, KARL SOHMIEDEL, a subject of the King of Saxony,residing at Charlottenburg, Germany, have invented certain new anduseful Improvements in Electric Meters, of which the following is aspecification.

My invention relates to electric meters, and particularly to alternatingcurrent induction meters.

More particularly my invention relates to induction meters having ashort-circuited coil or winding for producing the desired angle of phaselag or displacement between the torque-producing potential and currentfluxes.

The object of my invention is to provide in an induction electric meternovel means for rendering the phase angle between the torque-producingor motorial potential and I currentfiuXes substantially independent offrequency variations. 0

More particularly the ob ect of my invention is to provide novel meansacting in con-.

junction with a locally short-circuited phase lagging coil or winding ofan induction meter for compensating the angle of phase lag between themotorial potential and current fluxes for variations in frequency.

The novel features of my invention which I believe to be patentable andupon which I desire to secure Letters Patent are definitely indicated inthe claims appended hereto. These novel features of the invention,together with the construction and operation of an electric meterembodying the same, will be understood from the following clescriptiontaken in connection with the accompanying drawings, in which;

Figure 1 is a diagrammatic explanatory view of the magnetic circuit ofawell known type of induction electric meter; Fig. 2 is a vector diagramof the electrical and magnetic quantities of the magnetic circuit ofFig. 1'; Fig. 3 is a diagrammatic view of the magnetic circuit of aninduction electric meter embodying my presentinvention; Fig. 4c is avector diagram of the electrical and magnetic quantities of the magneticcircuit represented in Fig. 3; and Figs. 5, 6, 7 and 8 illustratemodified forms of the invention.

Alternating current electric meters of the induction type correctlyindicate orregister the load of an electrical installation only when themotorial magnetic fluxes of the potential or voltage circuit and -of thecurrent or load circuit are displaced in time phase from eachother by 90electrical degrees. By motorial magnetic flux, 1 mean a flux which iseffective in producing a turning or motor movement of the movableelement of the meter, or in other words, an effective torque-producingflux. The necessary phase displacement of 90 can be effected by alocally short-eircuited coil or winding which affects the motorial fluxof the potential circuit. The magnetic circuit of an induction meter ofthis type is diagrammatically illustrated in Fig. 1 of the drawings.

The magnetic circuit illustrated in Fig. 1 comprises a magnetic core ofthe usual laminated character having three legs or prongs 10, 11 and 12.Current coils 18 and 14, adapted to be connected in series relation withthe electrical installation whose energy consumption is to be metered,are

mounted on the outside legs 10 and 12 in the well known manner, while apotential coil, adapted to carry a current dependent upon' the voltageof such an electrical installation, is mounted on the middle leg 11.Bridges 16 and 17 of iron or similar magnetic material provide magneticshunts between the outer legs 10 and 12, respectively, and the middleleg 11 of the core. The magnetic shunting members 16 and 17 areseparated from the outer legs 10 and 12 by short air gaps 18 and 19,respectively. A locally short-circuited' coil or winding 20, comprisinga number of short-circuited turns or a single short-circuited turn, ismounted on the middle leg 11 above the magneticshunting bridges 16 and17. An armature 21 of magnetic material is operatively positioned abovethe triple-legged core, and is separated from'the middle leg by an, airgap 22 and from the outer legs "10 and 12 by air gaps 23 and 24:,respectively. It will be understood that the usual disk armature, ofcopper, aluminum, or equivalent material, of the movable element of themeter is rotatably mounted in the air gaps 22, 23 and 24.

The'paths 'of distribution of the magnetic flux through the magneticcircuit is shown in Fig. 1 by dotted'and by dash lines. The dotted linesshow the'paths of the flux due to-the load current flowing inwhole orin" part through the coils 13 and 14, While the dash lines shoW thepaths of the flux due to the current flowing in the potential coil 15.The paths of the stray fluxes are not indicated in the figure. Thepotential coil 15 develops a total flux Which We will call F. This totalflux F is composed of tvvo com ponents. One component F8 is the fluxwhich flows through the nearly closed magnetic circuit formed by theshunting bridges 16 and 17 and the outer legs 10 and 12 and may betermed the shunted potential flux. The second and relatively muchsmaller component Fe of the total flux F passes across the air gap 22into the magnetic armature 21 and returns through the air gaps 23 and24. and the outer legs 10 and 12. This second component Fe of the totalflux passes through the rotatable disk of the meter and is motorial,that is, elfective in producing a turning torque of the disk and may betermed the motorial or effective potential. flux. Since the component Fsof the total flux is shunted through the bridges 16 and 17, it isnon-motorial. The effective or motorial component Fe of the total fluxinduces an electromotive force in the locally shortcircuited coil 20Which causes an electric current to flow therein.

The time phase and distribution of the electrical and magneticquantities associated With the magnetic circuit represented in Fig. 1are vectorially indicated in Fig. 2. E represents the voltage impressedon the terminals of the potential Winding 15, and is henceforth referredto as the terminal voltage. The total flux F lags behind the terminalvoltage E in time phase by an angle substantially of the magnitudeindicated in the figure. The total flux is composed of the tWo componentfluxes F s and Fe, the latter considerably smaller in magnitude than theformer and having a considerably greater time phase angle of lag. Thetotal ampere turns, that is to say, the total magnetomotive force, ofthe potential Winding 15 is repre sented by M, and is obviously in timephase with the current flowing through the potential coil. The totalampere turns or magnetomotive force of the potential coil is dividedinto tWo components corresponding to the flux components F8 and Fe.Thus, M8 and Me represent the ampere turns or the magnetomotive forcesWhich are necessary to overcome the reluctances of the magnetic circuitsto the passage of the fluxes F8 and Fe, respectively. MsZ and Melrepresent the ampere turns or magnetomotive forces which are necessaryto overcome the iron and similar losses in the magnetic circuits throughWhich the fluxes M8 and Me, respectively, pass. Since the motorial andthe non-motorial magnetic circuits are in parallel, the

v vectorial sum of the magnetomotive forces in each circuit must be thesame, and each must be equal to the total magnetomotive force M. Themagnetomotive force Me, which acts to induce an electromotive force inthe short-circuited coil 20, must therefore combine vectorially with themagnetomotive forces Me and Mel to equal the total mag netomotive forceM. Ee is the electromotive force primarily causing the magnetic flux Fe,and Es is the electromotive force primarily causing the flux Fs. ThesetWo electromotive forces unite vertically With the ohmic drop in voltage2'1" of the potential circuit to produce the terminal voltage E.

The motorial fiuX Fe lags behind the terminal voltage E by an angle B.Since the electric circuit of the current coils 13 and 1a issubstantially non-inductive the current in these coils is substantiallyin phase with the voltage impressed thereon, and hence the magnetic fluxdeveloped by the coils 13 and 14 may be assumed to be in phase With theterminal voltage E. The angle B thus represents the angle of phase lagor displacement between the motorial potential and current fluxes. Itwill be observed from the vector diagram that the angle B can be alteredby varying the ampere turns or magnetomotive force Me which influencesthe short-circuited coil 15. Thus by proper dimensioning of theshort-circuited coil 15 the magnetomotive force, inducing anelectromotive force therein, can readily be made so large that themotorial flux Fe lags behind the terminal voltage E by an angle (13)equal to or greater than meters of this type the angle B variesconsiderably with variations in frequency. This makes the readings ofthe meter, for small phase displacement of the line current,considerably in error When there are slight variations of frequency. Theobject of my present invention is, therefore, to construct or arrangethe short-circuited coil so that even With large frequency variationsthe angle B remains substantially the same as for the normal frequency.

Assume for example that the frequency rises above the normal frequency.The induction in the iron and With it the magnetizing current and alsothe total current decrease, assuming of course that the terminal voltageE is maintained constant. The ohmic drop in Voltage i1" is reduced Whilethe angle of phase displacement B is greater than at normal frequency.It is, accordingly, most desirable and even necessary that somecompensation be provided for this increase in the phase angle caused byan increase in the frequency. In the present design of induction metersof this type the short-circuited coil 20 is so proportioned that itsohmic resistance exceeds its selfinductance. For regulating the angle ofphase displacement B, a Winding on the middle leg has, I believe, beenheretofore In induction '1 short-circuited through a variablenon-inductance resistance. WVith such an arrangement the phase of theSecondary ampere turns Mi remains practically unchanged. The abovementioned effect of the change in ir is also important, and as far as Iam aware, has not heretofore been compensated for. I have found if theshort-circuited coil 20 is so proportioned that its inductance isrelatively large with respect to its ohmic resistance, or if theshort-circuited. coil is closed through a selfinductance, or through acombination of inductance and ohmic resistance, that it is possible tomaintain the angle of phase displacement B practically constant with nomaterial change in its value even with large frequency variations.

The principle of my present invention is embodied in. the magneticcircuit diagrammatically represented in Fig. 3. Corresponding referencenumerals upon this figure represent corresponding elements described inconnection with Fig. 1. A number of turns of wire 20 are placed upon themiddle leg 11. The terminals of the coil or winding 20 are connected toa small selfinductance 25, consisting of a winding mounted upon amagnetic core 26 of iron or equivalent magnetic material. The magneticcore has an adjustable air gap whose width may be adjusted by a screw27. It will be obvious that the magnetic core 26 may be integrallyattached to the threelegged core of the main magnetic circuit or to themagnetic armature 21, and I have merely shown the core 26 as a separateunit for the purpose of explaining the principle of my invention.

The adjustable inductive winding or selfinductance 25 may be replaced bya combination of self-inductance 25 and non-inductive resistance 28, asdiagrammatically illustrated in Fig. 5. The inductive winding 25 and thenon-inductive resistance 28 may both be adjustable or non-adjustable asdesired or as conditions dictate.

In Fig. 6 I have shown the inductive winding divided into two coils 25".One coil 25 is electrically connected to the terminals of the phaselagging coil 20, while the other coil 25 is connected to an adjustableresistance 29. It will of course be un derstood that an adjustment mayalso be obtained in the usual way by making the turns of the coil 20variable.

Other practical modifications of the in vention are represented in Figs.7 and 8. In the embodiment of Fig. 7 a movable shortcircuited coil 20 issurrounded in sections or over its entire length by an iron or othermagnetic body 30. This enveloping of the short-circuited coil, either inwhole or in part, with magnetic material makes the selfinductance of thecoil large with respect to its ohmic resistance. In Fig. 8 the middleleg 11 of the principal magnetic circuit of the meter is provided withtwo slots 31 in which a short-circuited coil 20 is arranged, whereby theself-induction of the short-circuited coil is materially increased. Theshort-circuited coil can also be made entirely of iron and the correctvalue of the ratio of the self-induction to the ohmic resistance may beobtained by proper proportioning. In meters having several coils, thehereinbefore described arrangements may be correspondingly applied.

The vector diagram of Fig. 4 represents the time phases of theelectrical and mag netic quantities associated with the magnetic circuitof an induction meter constructed in accordance with my presentinvention as illustrated in Fig. 8. The secondary current flowing in thecoil 20, or in any equivalent locally short-circuited coil whoseelectric circuit has relatively large self-inductance with respect tothe ohmic resistance thereof, is very much displaced in time phase withrespect to the voltage causing the same. \Vith only small variations infrequency its phase changes considerably, and thereby compen satesperfectly the effect of the changein the ohmic drop in voltage 2'?" onthe angle of phase displacement B between the motorial potential andcurrent fluxes.

It will of course be understood that my invention is not limited to theparticular constructions and arrangements of elements herein illustratedand described. Thus, while I have explained my invention by illustratingand describing certain embodiments thereof, it will be understood bythose skilled in the art that the invention may be embodied in manyother forms than that shown and described. I, accordingly, do not wishto be restricted to the particular arrangements and constructionsdisclosed herein by way of example for the purpose of setting forth myinvention in accordance with the patent statutes. The terms of theappended claims are, therefore, not restricted to the precise structuresherein disclosed, but are intended to cover all changes andmodifications thereof within the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the'UnitedStates is,-

1. In an induction electric meter, means for producing a current fluxand a potential flux, a short-circuited coil for displacing the timephase of the potential flux with respect to that of the current fiuX,and means cooperating with said coil for compensating the angle of phasedisplacement between the current and potential fluxes for variations infrequency.

2. In an induction electric meter, means for producing a current fiuXand a potential flux, a magnetic circuit providing two paths for thepotential flux whereby a part of said potential flux is efieetive and apart noneffective, a short-circuited coil for displacing the time phaseof the effective component of the potential flux With respect to that ofthe current firm, and means cooperat ing with said coil for maintainingthe angle of phase displacement between the effective potential andcurrent fluxes substantially constant and independent of variations infrequency.

3. In an induction electric meter, means for producing a current fluxand a potential flux, a magnetic circuit providing two paths for thepotential flux whereby a part of said potential flux is effective and apart noneffective, a short-circuited coil for displacing the time phaseof the effective component of the potential flux with respect to that ofthe current flux, and means for imparting to the circuit of said coil arelatively large self-inductance with respect to the ohmic resistancethereof.

4. In an induction electric meter, means for producing a current fluxand a potential flux, a magnetic circuit providing two paths for thepotential flux whereby a part of said potential flux is effective and apart noneffective, a short-circuited coil for displacing the time phaseof the effective component of the potential flux with respect to that ofthe current flux, an inductance connected in the circuit with said coil,and means for adjusting the inductance of the electric circuit includingsaid coil and said inductance.

5. In an "induction electric meter, means for producing a current fluxand a potential flux, a magnetic circuit providing two paths for thepotential flux whereby a part of said potential flux is effective and apart noneffective, a short-circuited coil for displacing the time phaseof the effective component of the potential flux with respect to that ofthe current flux and an inductance and a non-inductive resistanceelectrically connected to said coil.

In witness whereof, I have hereunto set my hand this 5th day ofNovember, 1914.

KARL SCHMIEDEL. Witnesses:

AUGUST Moon, l/VALTER COHN-BYK.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents. Washington, D. 0.

